One small item left abandoned — a common roadside sight (9)
I believe the answer is:
milestone
'common roadside sight' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'one small item left abandoned a' is the wordplay.
'one small item' becomes 'mile' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'left' becomes 'split' (split can mean to run away or leave).
'abandoned' says to hollow out the word (remove centre letters) (middle letters abandon or vacate the word).
'a' becomes 'one'.
'split' with its centre removed is 'st'.
'mile'+'st'+'one'='MILESTONE'
Can you help me to learn more?
(Other definitions for milestone that I've seen before include "Wayside indicator" , "Pillar" , "Significant event or stage - a measure" , "Significant developmental stage" , "Roadside distance marker" .)